1. Field of the Invention
The present invention relates to lighting devices and, more specifically, to lighting devices, components of such lighting devices, and methods for their manufacture. The apparatus and methods of the invention are particularly well suited for application in gas discharge lighting devices such as neon and fluorescent lighting, and in incandescent lighting.
2. Description of the Related Art
Incandescent lighting devices have been known and used for years. These lighting devices comprise a glass bulb or tube which is sealed to form an envelope. A filament inside the envelope is electrically excited to produce light.
Gas discharge lighting devices have been in commercial use for most of the twentieth century. Examples of gas discharge lighting devices include neon lighting, fluorescent lighting, and the like. Such devices have enjoyed relatively widespread use in applications such as lighting, illuminated signage and decorative works for residential, commercial and industrial uses.
The design and operation of gas discharge lighting devices has been well known for years. See, e.g., Samuel C. Miller, Neon Techniques & Handling, Signs of the Times Publishing Co., Cincinnati, Ohio (1977). The devices typically include a sealed envelope comprising a glass tube with metal electrodes at opposing ends. A gas mixture typically including a noble or inert gas, such as neon, and mercury vapor is contained within the envelope and maintained at low pressure. In operation, electrical energy typically in the form of a high-voltage, alternating current is passed through the gas mixture using the electrodes. This electromagnetic energy passing through the gas mixture causes electrons to be liberated from the gas molecules, which accelerates the ionized plasma particles toward the respective electrodes. The plasma particles collide with other gas molecules, which generate additional ions. The net effect is an avalanching of charged particles being generated and recaptured. As the ions are recaptured, energy is emitted from them in the form of light of various wavelengths, including visible and ultraviolet ("UV") wavelengths. In the case of visible light emission, illumination from the device is direct. With UV emission from mercury vapor, visible light is produced by a phosphor coating on the tube interior by fluorescence stimulated by the UV. Traditionally the tubing for such lighting has been formed of various types and grades of glass. Examples of glasses used in neon and fluorescent tubing have included lead glasses and lime or soda glasses.
Glass envelope materials have been disadvantageous, for example, in their brittleness and susceptibility to breakage. Their brittleness also has had the disadvantageous effect of preventing the manufacture of bulbs or tubing which has sharp angles, particularly in their cross sectional geometry. The composition, structure and properties of glass also have limited the ability to bond the glass to other materials while maintaining the pressure ranges and tolerances required for effective gas discharge lighting over the range of operating conditions typically encountered by such devices.
In some instances manufacturers of lighting devices have used coating materials or sheathing to coat or otherwise support the glass envelopes. For example, traditional neon lighting glass envelopes have been provided with an exterior coating of a transparent polymer-based material to resist breakage.
The use of coating materials also has been subject to drawbacks. Although such coating materials in some instances have afforded greater structural strength to the glass bulbs or tubing, this added strength still has usually been inadequate. A sharp impact on the exterior of the envelope, even with the coating, in many cases can crack or break the envelope and compromise the vacuum integrity of the envelope interior. Moreover, the use of such coatings has added significantly to the cost and difficulty of manufacturing the devices.
Traditional methods for coupling lighting devices to a power source cable such as a GTO wire also have been limited. The wire typically would be connected or fastened using a screw or similar fastener. Attaching and detaching the wires using this method has been cumbersome, time consuming and inefficient.